The Michigan election law enacted by last session’s Senate Bill 571 is facing yet another legal challenge. A group of labor unions filed suit against the State of Michigan claiming that the law is unconstitutional.

The contested provision of the law allows corporations to use payroll deductions for employees to make contributions to the business’ political action committee (PAC). The unions claim this is unfair because they are prohibited from using payroll deductions for members to make contributions to union PACs.

The lawsuit comes just weeks after a federal judge in a separate matter found other provisions of this law unconstitutionally vague.